Further simplify unstoppable (#938)

[stockfish] / src / evaluate.cpp

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index c37bd26f9c32b81c8da16692ddb5a40a480be4ee..19bfc9fe299820f3c4a95beeb2845f77892a2e47 100644 (file)
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -194,11 +194,12 @@ namespace {
   const Score OtherCheck          = S(10, 10);
   const Score ThreatByHangingPawn = S(71, 61);
   const Score LooseEnemies        = S( 0, 25);
-  const Score WeakQueen           = S(35,  0);
+  const Score WeakQueen           = S(50, 10);
   const Score Hanging             = S(48, 27);
   const Score ThreatByPawnPush    = S(38, 22);
-  const Score Unstoppable         = S( 0, 20);
   const Score PawnlessFlank       = S(20, 80);
+  const Score HinderPassedPawn    = S( 7,  0);
+  const Score ThreatByRank        = S(16,  3);
 
   // Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
   // a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
@@ -347,7 +348,6 @@ namespace {
                 Square ksq = pos.square<KING>(Us);
 
                 if (   ((file_of(ksq) < FILE_E) == (file_of(s) < file_of(ksq)))
-                    && (rank_of(ksq) == rank_of(s) || relative_rank(Us, ksq) == RANK_1)
                     && !ei.pi->semiopen_side(Us, file_of(ksq), file_of(s) < file_of(ksq)))
                     score -= (TrappedRook - make_score(mob * 22, 0)) * (1 + !pos.can_castle(Us));
             }
@@ -560,11 +560,21 @@ namespace {
     {
         b = (defended | weak) & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
         while (b)
-            score += Threat[Minor][type_of(pos.piece_on(pop_lsb(&b)))];
+        {
+            Square s = pop_lsb(&b);
+            score += Threat[Minor][type_of(pos.piece_on(s))];
+            if (type_of(pos.piece_on(s)) != PAWN)
+                score += ThreatByRank * (int)relative_rank(Them, s);
+        }
 
         b = (pos.pieces(Them, QUEEN) | weak) & ei.attackedBy[Us][ROOK];
         while (b)
-            score += Threat[Rook ][type_of(pos.piece_on(pop_lsb(&b)))];
+        {
+            Square s = pop_lsb(&b);
+            score += Threat[Rook][type_of(pos.piece_on(s))];
+            if (type_of(pos.piece_on(s)) != PAWN)
+                score += ThreatByRank * (int)relative_rank(Them, s);
+        }
 
         score += Hanging * popcount(weak & ~ei.attackedBy[Them][ALL_PIECES]);
 
@@ -601,7 +611,7 @@ namespace {
 
     const Color Them = (Us == WHITE ? BLACK : WHITE);
 
-    Bitboard b, squaresToQueen, defendedSquares, unsafeSquares;
+    Bitboard b, bb, squaresToQueen, defendedSquares, unsafeSquares;
     Score score = SCORE_ZERO;
 
     b = ei.pi->passed_pawns(Us);
@@ -613,6 +623,9 @@ namespace {
         assert(pos.pawn_passed(Us, s));
         assert(!(pos.pieces(PAWN) & forward_bb(Us, s)));
 
+        bb = forward_bb(Us, s) & (ei.attackedBy[Them][ALL_PIECES] | pos.pieces(Them));
+        score -= HinderPassedPawn * popcount(bb);
+
         int r = relative_rank(Us, s) - RANK_2;
         int rr = r * (r - 1);
 
@@ -638,7 +651,7 @@ namespace {
                 // in the pawn's path attacked or occupied by the enemy.
                 defendedSquares = unsafeSquares = squaresToQueen = forward_bb(Us, s);
 
-                Bitboard bb = forward_bb(Them, s) & pos.pieces(ROOK, QUEEN) & pos.attacks_from<ROOK>(s);
+                bb = forward_bb(Them, s) & pos.pieces(ROOK, QUEEN) & pos.attacks_from<ROOK>(s);
 
                 if (!(pos.pieces(Us) & bb))
                     defendedSquares &= ei.attackedBy[Us][ALL_PIECES];
@@ -664,6 +677,10 @@ namespace {
                 mbonus += rr + r * 2, ebonus += rr + r * 2;
         } // rr != 0
 
+        // Assign a small bonus when no pieces left (unstoppable)
+        if (!pos.non_pawn_material(Us) && !pos.non_pawn_material(Them))
+            ebonus += 20;
+
         score += make_score(mbonus, ebonus) + PassedFile[file_of(s)];
     }
 
@@ -838,17 +855,6 @@ Value Eval::evaluate(const Position& pos) {
   score +=  evaluate_passed_pawns<WHITE, DoTrace>(pos, ei)
           - evaluate_passed_pawns<BLACK, DoTrace>(pos, ei);
 
-  // If both sides have only pawns, score for potential unstoppable pawns
-  if (!pos.non_pawn_material(WHITE) && !pos.non_pawn_material(BLACK))
-  {
-      Bitboard b;
-      if ((b = ei.pi->passed_pawns(WHITE)) != 0)
-          score += Unstoppable * int(relative_rank(WHITE, frontmost_sq(WHITE, b)));
-
-      if ((b = ei.pi->passed_pawns(BLACK)) != 0)
-          score -= Unstoppable * int(relative_rank(BLACK, frontmost_sq(BLACK, b)));
-  }
-
   // Evaluate space for both sides, only during opening
   if (pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK) >= 12222)
       score +=  evaluate_space<WHITE>(pos, ei)
@@ -873,8 +879,9 @@ Value Eval::evaluate(const Position& pos) {
       Trace::add(IMBALANCE, ei.me->imbalance());
       Trace::add(PAWN, ei.pi->pawns_score());
       Trace::add(MOBILITY, mobility[WHITE], mobility[BLACK]);
-      Trace::add(SPACE, evaluate_space<WHITE>(pos, ei)
-                      , evaluate_space<BLACK>(pos, ei));
+      if (pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK) >= 12222)
+          Trace::add(SPACE, evaluate_space<WHITE>(pos, ei)
+                          , evaluate_space<BLACK>(pos, ei));
       Trace::add(TOTAL, score);
   }